In electrical products, it is necessary to use different flashing lights to represent different operation situations. In FIG. 1, a low pulse signal 100 controls a switching device 104 that makes a light emitting diode 102 flash.
Typically, there are two methods of generating the low pulse signal 100. One is to use a program to control a counter in a CPU to output the pulse signals from the general purpose input/output pins. The pulse signals make the switching devices switch the light emitting diodes on/off. However, the CPU has to keep working in this method, which increase the power consumption of the electrical products. Additionally, the working efficiency of the CPU is reduced because the partial calculation period is used to generate the pulse signals.
Another method is to use an oscillation circuit to generate pulse signals with a fixed period to make the switching device switch the light emitting diodes on/off. However, an additional oscillation circuit is required in this method, which increase the cost and the volume of the electrical products. Moreover, the oscillation circuit can only generate a pulse signal with a fixed period. Therefore, the flashing period is also fixed, which limits the application range thereof.
A pulse signal generator inside a CPU is typically used to resolve the problem of fixed period resulting from use of the oscillation circuit. This pulse signal generator is used to provide a pulse signal whose period is modulated by the CPU. However, although this method can resolve the fixed period problem, a pulse signal generator can only provide a pulse signal. In other words, the number of flashing lights is related to the number of pulse signal generators inside a CPU. If the number of pulse signal generators built in a CPU is not enough, an additional pulse signal generator must be attached to the CPU, which increase the manufacturing cost and the volume of a electrical product.